In physical science disciplines, such as that of quantum mechanics and particle physics, a spin magnetic moment may be defined as the magnetic moment induced by the spin of elementary particles, such as an electron or a nucleus of a nuclear particle. In this context, “spin” may be a non-classical property of elementary particles, because classically, the “spin” of a material object may be defined as the total orbital angular momentum of constituents of the material object about a rotational axis of the material object. Elementary particles however, may be conceived as points, and may therefore not have an axis to “spin” about.
The magnetic moment induced by the spin of the elementary particle may be defined in terms of an electric current and the area enclosed by a loop of the electric current. Since angular momentum corresponds to rotational motion, the magnetic moment may be related to the orbital angular momentum of the charge carriers constituting the current. Further, in magnetic materials, atomic and molecular dipoles may have magnetic moments due to the spin of elementary particles constituting the magnetic material in addition to any quantized orbital angular momentum present. In fact, in some cases an elementary particle may not necessarily have electric charge to have a spin magnetic moment. For instance, a neutron, despite being electrically neutral, may have a non-zero magnetic moment due to an internal quark structure of the neutron.
In the context of the present application, electron spin may refer to an intrinsic angular momentum of an electron, and a nuclear spin may refer to an angular momentum of the nucleus of a nuclear particle, as briefly discussed above.